GPS广域增强系统的研究与实现

最初由美国FAA提出的广域增强系统（WAAS）的概念,主要用来满足航空领域对GPS导的要求,广域增强系统包括由分布在广大区域上的参考站组成的网络,中心站,上行站以及地球同步轨道卫星等部分,本文试图对广域增强系统的组成结构。基本算法及其特点加以阐述,并对广域增强系统在我国的建设提出初步的设想。     

我国广域增强系统的基准站布局及数量分析

广域增强系统可以提高GPS系统的导航和定位精度,满足不同用户的需求,其基准站的布局和数量对提高系统的性能和实施有着重要的意义。通过对基准站上空的格网内的电离层穿透点个数进行统计分析,讨论了我国广域增强系统基准站的布局与数量问题。     

浅析WAAS完好性算法

广域增强系统完好性是度量系统时空可用性的关键指标,它关系到用户所获得的改正信息是否真实可靠。在阐述广域增强系统完好性定义的基础上,对完好性算法流程、思路进行了分析。     

EGNOS电离层延迟改正数分析

EGNOS是一个广域增强系统,向用户提供电离层改正数是其服务内容的一部分。本文分析了EGNOS电离层改正数的结构,介绍了用户的电离层改正数算法流程。结合EGNOS在中国测试的实际数据,对EGNOS电离层改正数进行了分析。通过对EGNOS的电离层改正数分析可以为我国的广域增强系统提供技术参考。     

建立中国差分GPS实时定位系统的思考

介绍了局域和广域差分ＧＰＳ及其增强系统的技术特点,在此基础上讨论了在中国建立广域差分ＧＰＳ实时定位系统的重要意义,以及有关问题的思考。     

北斗系统的特色、机遇与挑战

北斗系统是我国自主建设的卫星导航系统,已经具备了亚太大部分地区的区域服务能力。在对北斗系统的基本性能、发展步骤、系统组成等进行简介的基础上,主要阐述了北斗系统的特色,即独特的混合星座、导航定位与通信集成、导航定位与广域差分增强的融合等。重点分析了全球背景下我国北斗系统面临的机遇与挑战。     

浅析WAAS电离层延迟网格修正算法

阐述了广域增强系统电离层延迟网格修正算法流程、思路及特点,希望能给相关研究者提供参考.     

打造覆盖全球的星基增强服务系统——记合众思壮创新提升北斗全球竞争力

正星基增强服务系统(satelite based augmentation systems;SBAS),也叫广域差分增强系统,是一种通过卫星向用户播发星历误差、卫星钟差、电离层延迟等多种修正信息,实现对于原有卫星导航系统定位精度的改进增强手段。目前全球发展的S B A S系统主要有欧空局接收卫星导航系统(EGNOS),覆盖欧洲大陆;美国的DGPS(Differential GPS)和广域增     

星基增强系统“中国精度”与CORS网的对比分析

随着"数字城市"建设的进行,CORS网已经成为城市空间数据基础设施的重要组成部分,在高精度测量和位置服务中起到越来越重要的作用;而GNSS广域差分星基增强系统却没有得到快速的发展和大量的应用,普及范围远远不够。在此背景下,介绍了中国首套GNSS广域差分星基增强系统"中国精度",并对比分析了"中国精度"(Atlas)与CORS的差异与协作等。     

广域增强系统的数据验证结构与方法

分析了广域增强系统中的数据验证结构.数据验证结构的基本条件是每个参考站有2台独立的接收机.在主站上,来自2台接收机的2条数据流分别送入2套处理设备中,构成3层验证结构来验证系统的出站数据.此结构与方法利用平行运行的硬件和软件进行多点不同途径的验证,以提高广域增强系统故障定位与分离能力.     

Android平台下实时BDS+GPS双系统广域差分定位技术研究

随着智能手机的普及,基于移动智能终端的位置服务应用正在飞速扩张。Android智能终端,因其性价比高而占据了大多数用户市场,但定位精度有待提升。因此,利用广域差分增强技术,提升室内外位置服务精度,成为当前研究热点。本文利用Android studio 2.2.2平台、Java语言及JNI技术,开发了BDS+GPS广域差分定位软件,该软件通过串口读取北斗移动终端原始卫星观测数据,进行差分数据流解析、实时轨道和钟差改正并实现增强定位。在移动终端硬件平台上,运行BDS+GPS实时WAAS软件,分析了定位结果,双系统单频广域定位精度为4 m左右,对于GNSS卫星技术在低成本移动终端位置服务中具有重要应用价值。     

SBAS orbit and satellite clock corrections for precise point positioning

The quality of real-time GPS positions based on the method of precise point positioning (PPP) heavily depends on the availability and accuracy of GPS satellite orbits and satellite clock corrections. Satellite-based augmentation systems (SBAS) provide such corrections but they are actually intended to be used for wide area differential GPS with positioning results on the 1-m accuracy level. Nevertheless, carrier phase-based PPP is able to achieve much more accurate results with the same correction values. We applied SBAS corrections for dual-frequency PPP and compared the results with PPP obtained using other real-time correction data streams, for example, the GPS broadcast message and precise corrections from the French Centre National d’Etudes Spatiales and the German Deutsches Zentrum für Luft- und Raumfahrt. Among the three existing SBAS, the best results were achieved for the North American wide area augmentation system (WAAS): horizontal and vertical position accuracies were considerably smaller than 10 cm for static 24-h observation data sets and smaller than 30 cm for epoch-by-epoch solutions with 2 h of continuous observations. The European geostationary navigation overlay service and the Japanese multi-functional satellite augmentation system yield positioning results with biases of several tens of centimeters and variations larger by factors of 2–4 as compared to WAAS.     

综合PNT场景增强系统研究进展及发展趋势

定位导航授时（positioning navigation and timing,PNT）是国家重要战略基础设施,目前中国已经建立了完善的北斗天基增强系统、地基增强系统、低轨增强系统,室内外定位技术蓬勃发展,但声光电磁等多种定位技术手段在全球导航卫星系统（global navigation satellite system,GNSS）拒止环境受到诸多限制,在深空、深地、深海三深空间综合PNT依然面临许多困难。近年来,数字孪生、实景三维等战略逐渐落地,三维场景为提高综合PNT的完好性、连续性、可用性提供了新的机遇。对综合PNT场景增强国内外技术现状进行了系统梳理,总结了综合PNT场景增强系统面临的挑战,阐述了综合PNT场景增强系统建设主体、服务层次、系统架构等基本框架,展望未来中国的综合PNT体系是以北斗PNT为核心,天基增强、地基增强、低轨增强、场景增强多源信息集成的服务于全空间的综合PNT智能服务体系。     

GPS现代化和GPS信号重构技术的进展

介绍了GPS现代化计划和GPS信号重构技术的进展。GPS信号重构的目的是确保在某些特定区域的美军能够正常使用GPS而不受影响,而在同一区域与美军对立的一方既不能使用民用GPS信号,也不能使用GPS的军码,至于在该特定区域以外的民间GPS用户,则依然能够正常使用GPS;此外还重点介绍了由美国大地测量局(NGS)主持运行的GPS陆基增强系统(CORS)。     

精度和完备性在GALILEO局域监测网中变化规律研究

完备性是飞机飞行安全的重要指标之一。本文在网形固定的情况下,利用GALIEO模拟数据,计算飞机的精度和垂直保护水平(VPL),并分析飞机在监测网中不同位置时,精度和垂直保护水平的的变化规律,得到影响精度和垂直保护水平的因素。     

北斗广域差分分区综合改正数定位性能分析

目前北斗广域分米级星基增强系统在钟差改正数、轨道改正数的基础上,提出了基于相位观测值的分区综合改正数,介绍了分区综合改正数的概念及单频、双频用户的使用方法与定位模型。利用中国范围不同地区的北斗观测数据和对应的分区综合改正信息,统计了单频和双频用户分区综合改正精密单点定位的精度,并对其收敛性进行了分析。通过与使用GFZ提供的北斗超快速精密星历的定位效果比较,验证了分区综合改正定位在实时定位中的优势。在此基础上进一步对中国范围内分区综合改正定位效果与分区中心距离的关系进行了分析,并对不同观测时间长度的定位效果进行比较。结果表明,经分区综合改正后的双频用户平均25 min内动态定位三维误差能收敛至0.5 m以内,收敛后的定位精度为水平0.15 m,高程0.2 m;单频用户平均20 min内动态定位三维误差能收敛至0.8 m以内,收敛后的定位精度为水平0.3 m,高程0.5 m。随着用户站距离分区中心越远,定位效果总体呈现变差的趋势。总体上,当用户在分区中心1 000 km范围内时,北斗广域分区综合改正数将能提供实时分米级定位服务。     

Virtual differential GPS based on SBAS signal

In order to access the satellite-based augmentation system (SBAS) service, the end user needs access to the corresponding geostationary earth orbit (GEO) satellites that broadcast the augmentation information for the region. This is normally not a problem for aviation and maritime applications, because an open sky is typically available for such applications. However, it is difficult to access the GEO satellites directly at high latitudes for land applications because of the low elevation angles to the GEO satellites (e.g., 4–22° in Finland to the European geostationary navigation overlay services [EGNOS] GEO satellites). Results from a driving test of 6,100 km in Finland show that the EGNOS GEO satellites can be accessed in only 51.8% of the driving routes. Furthermore, it is also difficult to access the GEO satellites from city canyons, because the high buildings block the GEO signals. This article presents a solution to solve this problem by creating virtual differential GPS (DGPS) reference stations using the SBAS signal in space (SIS). The basic concept is to convert the SBAS signal to Radio Technical Commission for Maritime Services (RTCM) signals, and broadcast the converted RTCM signals over the wireless Internet using the Internet radio technology. Therefore, access to the SBAS service will not be limited by low elevation angles to the GEO satellites because the converted RTCM data streams are disseminated over the wireless Internet. Furthermore, the SBAS service can then be accessed via a legacy DGPS receiver. Two test cases have been carried out with the prototype system developed by the Finnish Geodetic Institute. The test results showed that the positioning accuracy of the virtual DGPS solution was about 1–2 m at 95%, which was similar to that of the standard WAAS/EGNOS solution. The positioning accuracy was not degraded, compared to that of the standard wide area augmentation system–European geostationary navigation overlay services (WAAS/EGNOS) solution, as long as the distance between the rover receiver and the virtual DGPS reference station was less than 150 km. A preliminary driving test of 400 km carried out in southern Finland showed that the availability of the virtual DGPS solutions was 98.6% along the driving route.     

Galileo Constellation Design

A significant effort has been carried out in Europe to define the European Global Navigation Satellite System (GNSS), named Galileo Satellites flying in Medium Earth Orbits (MEO) will compose the system (according to the most recent architecture definition baseline); a regional complement of geosynchronous satellites may be required to increase performances over Europe and maybe also to provide some specific communication services. Nominal medium performances are envisaged, but they will be increased by means of augmentation systems (local or wide area), or even by using simultaneously other GNSSs such as GPS. All the involved requirements make the design process quite complex. A powerful software tool, Elcano, has been developed for this purpose; its capabilities will be outlined, and the results of the design process will be presented. ? 2001 John Wiley & Sons, Inc.